package j03tongpeifu;
class Ye{}
class Fa extends Ye{}
class Ch extends Fa{}

class C<T>{}

public class J1 {
    public static void main(String[] args) {
        //限定通配符的上界
        C<? extends Fa> c1 = new C<Fa>();
        C<? extends Fa> c2 = new C<Ch>();
//        C<? extends Fa> c3 = new C<Ye>();

        //限定下届
        C<? super Fa> cc1 = new C<Fa>();
        C<? super Fa> cc2 = new C<Ye>();
        C<? super Fa> cc4 = new C<Object>();
//        C<? super Fa> cc3 = new C<Ch>();

    }
}
